Railroads are under increasing pressure to reduce emissions and fuel consumption. One of several responses to these forces has been the development of hybrid locomotives. Donnelly has disclosed the use of a battery-dominant hybrid locomotive in U.S. Pat. No. 6,308,639 which is incorporated herein by reference. Hybrid locomotives can reduce emissions and fuel consumption in many rail situations such as yard switching but they are less effective for medium haul freight or commuter trains.
In the search for efficient engine and fuel strategies, many different power plant and power delivery strategies have been investigated. Some of these have involved approaches which attempt to synchronize multiple engines of the same type or to utilize different fuels for the same engine. Other strategies involve combinations of conventional and hybrid locomotives in a consist.
Donnelly has also disclosed a method and apparatus for controlling power provided to DC traction motors by furnishing an individual chopper circuit for each traction motor in U.S. Pat. No. 6,812,656 which is incorporated herein by reference. Donnelly et al. have disclosed a method of monitoring, synchronizing and optimizing the operation of the locomotive drive train in U.S. patent application Ser. No. 10/649,286; have also disclosed a method of allocating energy amongst members of a consist in U.S. patent application Ser. No. 11/070,848; and have disclosed a method for monitoring, controlling and/or optimizing the emission profile for a hybrid locomotive or consist of hybrid locomotives in U.S. patent application Ser. No. 11/095,036, all of which are also incorporated herein by reference.
In U.S. Provisional Applications 60/607,194 and 60/618,632, Donnelly et al. have further disclosed a general electrical architecture for locomotives based on plurality of power sources, fuel and drive train combinations. The power sources may be any combination of engines, energy storage and regenerative braking. Donnelly et all have also disclosed a versatile multiple engine control strategy that can by applied to locomotives to reduce emissions and fuel consumption in U.S. Provisional Application 60/674,837. These provisional applications are also incorporated herein by reference.
Multi-engine locomotives are not new. Often a multi-engine locomotive can be comprised of engines each of which can provide power to separate driving wheel assemblies or separate groups of driving wheel assemblies. In other designs, the AC electrical output of two engine/alternator systems have been synchronized to provide power to an AC bus which, in turn, provides power to all the locomotive's traction motors. Older multi-engine designs have utilized synchronized mechanical transmissions to supply power directly to the driving wheel assemblies.
Recently, a French Railway Company, VFLI, disclosed a dual engine locomotive utilizing a common DC bus electrical transmission where the two engines need not be synchronized. The second engine in this design is brought on-line using a simple algorithm. Under this algorithm, when the power output of the first engine exceeds 70% of its rated value, the second engine is brought on-line.
However, there remains a need for a versatile multiple engine packaging strategy that optimizes the power density of the locomotive power plant while reducing emissions and fuel consumption.